Branch communication valve for a twin scroll turbocharger

ABSTRACT

Methods and systems are provided for a branch communication valve in a twin turbocharger system. A branch communication valve may be positioned adjacent to a dividing wall separating a first scroll and a second scroll of the twin turbocharger. In an open position, the branch communication valve increases fluid communication between the first scroll and the second scroll and in a closed position, the branch communication valve decreases fluid communication between the first scroll and the second scroll.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/621,971, entitled “BRANCH COMMUNICATION VALVE FOR A TWINSCROLL TURBOCHARGER,” filed on Jun. 13, 2017. U.S. patent applicationSer. No. 15/621,971 is a divisional of U.S. patent application Ser. No.14/727,563, entitled “BRANCH COMMUNICATION VALVE FOR A TWIN SCROLLTURBOCHARGER,” filed on Jun. 1, 2015, now U.S. Pat. No. 9,677,460. U.S.patent application Ser. No. 14/727,563 is a divisional of U.S. patentapplication Ser. No. 13/829,599, entitled “BRANCH COMMUNICATION VALVEFOR A TWIN SCROLL TURBOCHARGER,” filed Mar. 14, 2013, now U.S. Pat. No.9,068,501. U.S. patent application Ser. No. 13/829,599 claims priorityto U.S. Provisional Patent Application No. 61/759,888, entitled “BRANCHCOMMUNICATION VALVE FOR A TWIN SCROLL TURBOCHARGER,” filed on Feb. 1,2013. The entire contents of the above-referenced applications arehereby incorporated by reference in their entirety for all purposes.

BACKGROUND/SUMMARY

Twin scroll turbocharger configurations may be used in turbochargedengines. A twin scroll turbocharger configuration may separate an inletto a turbine into two separate passages connected to exhaust manifoldrunners so that exhaust from engine cylinders whose exhaust gas pulsesmay interfere with each other are separated.

For example, on an I4 engine with a cylinder firing order of 1-3-4-2,exhaust manifold runners 1 and 4 may be connected to a first inlet of atwin scroll turbine and exhaust manifold runners 2 and 3 may beconnected to a second inlet of said twin scroll turbine, where thesecond inlet is different from the first inlet. Separating exhaust gaspulses in this way may, in some examples, result in an increase inefficiency of exhaust gas delivery to a turbine.

However, the inventors herein have recognized that under some engineoperating conditions separating exhaust gas pulses as described abovemay reduce an efficiency of exhaust gas delivery to a turbine. Forexample, the inventors herein have recognized that under certain engineoperating conditions, e.g., high speed and high load conditions,separating exhaust gas pulses as described above may result in anincrease in backpressure and pumping work due to, for example, anincrease in exhaust gas enthalpy.

In one example, the issues described above may be addressed bypositioning a branch communication valve between a first scroll and asecond scroll in a twin (e.g., dual) turbocharger scroll system. In oneexample, the first scroll and the second scroll may be fluidicallyseparated by a dividing wall. A passage may be positioned verticallyabove the dividing wall and bridge the first scroll and the secondscroll. The branch communication valve may be positioned within thepassage. In an open position, exhaust flowing through the first andsecond scrolls may enter the passage and flow into the opposite scroll.In a closed position, the branch communication valve may seal against anopening between the passage and the first and the second scrolls,thereby reducing fluid communication between the scrolls.

In another example, a branch communication valve may be positionedwithin and/or adjacent to the dividing wall. The branch communicationvalve may be movable between an open and closed position. In a closedposition, a portion of the branch communication valve may cover and sealagainst a hole or opening in the dividing wall. In an open position, thehole or opening may be exposed such that fluid communication between thefirst and second scrolls increases.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of an engine including a twin scrollturbocharger and a branch communication valve.

FIG. 2 shows a first embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 3 shows a second embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 4 shows a third embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 5 shows a fourth embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 6 shows a fifth embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 7 shows a sixth embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 8 shows a seventh embodiment of a branch communication valve for atwin scroll turbocharger system.

FIG. 9 shows an eighth embodiment of a branch communication valve for atwin scroll turbocharger system.

DETAILED DESCRIPTION

The following description relates to a branch communication valve tocontrol fluid communication between a first and second scroll in a twinor dual scroll turbocharger system. As shown in FIG. 1, a first scrolland a second scroll may be fluidically separated by a dividing wall. Assuch, exhaust gases from different engine cylinders may be routed intoseparate passages connecting to the first and second scrolls. This mayallow separation of different, and potentially interfering, exhaust gaspulses before entering a turbine, thereby increasing exhaust gasdelivery to the turbine and increasing engine efficiency. However, undercertain engine operating conditions, separating the exhaust gas pulsesmay reduce engine efficiency. Under these conditions, increased fluidcommunication between the first and second scrolls may be desired. Thus,a branch communication valve may be used to increase or decrease fluidcommunication between the first and second scrolls. For example, thebranch communication valve may be positioned within or adjacent to thedividing wall. Opening the branch communication valve may allowincreased fluid communication between the first and second scrolls,while closing the branch communication valve may reduce fluidcommunication between the first and second scrolls. Differentembodiments of the branch communication valve are presented at FIGS.2-9.

Turning now to FIG. 1, a schematic diagram of an engine 10, which may beincluded in a propulsion system of an automobile, is shown. Engine 10may be controlled at least partially by a control system includingcontroller 12 and by input from a vehicle operator 14 via an inputdevice 16. In this example, input device 16 includes an acceleratorpedal and a pedal position sensor 18 for generating a proportional pedalposition signal PP.

Engine 10 may include a plurality of combustion chambers (i.e.,cylinders). In the example shown in FIG. 1, Engine 10 includescombustion chambers 20, 22, 24, and 26, arranged in an inline 4configuration. It should be understood, however, that though FIG. 1shows four cylinders, engine 10 may include any number of cylinders inany configuration, e.g., V-6, I-6, V-12, opposed 4, etc.

Though not shown in FIG. 1, each combustion chamber (i.e., cylinder) ofengine 10 may include combustion chamber walls with a piston positionedtherein. The pistons may be coupled to a crankshaft so thatreciprocating motions of the pistons are translated into rotationalmotion of the crankshaft. The crankshaft may be coupled to at least onedrive wheel of a vehicle via an intermediate transmission system, forexample. Further, a starter motor may be coupled to the crankshaft via aflywheel to enable a starting operation of engine 10.

Each combustion chamber may receive intake air from an intake manifold28 via an air intake passage 30. Intake manifold 28 may be coupled tothe combustion chambers via intake ports. For example, intake manifold28 is shown in FIG. 1 coupled to cylinders 20, 22, 24, and 26 via intakeports 32, 34, 36, and 38 respectively. Each respective intake port maysupply air and/or fuel to the respective cylinder for combustion.

Each combustion chamber may exhaust combustion gases via an exhaust portcoupled thereto. For example, exhaust ports 40, 42, 44 and 46, are shownin FIG. 1 coupled to cylinders 20, 22, 24, 26, respectively. Eachrespective exhaust port may direct exhaust combustion gases from arespective cylinder to an exhaust manifold or exhaust passage.

Each cylinder intake port can selectively communicate with the cylindervia an intake valve. For example, cylinders 20, 22, 24, and 26 are shownin FIG. 1 with intake valves 48, 50, 52, and 54, respectively. Likewise,each cylinder exhaust port can selectively communicate with the cylindervia an exhaust valve. For example, cylinders 20, 22, 24, and 26 areshown in FIG. 1 with exhaust valves 56, 58, 60, and 62, respectively. Insome examples, each combustion chamber may include two or more intakevalves and/or two or more exhaust valves.

Though not shown in FIG. 1, in some examples, each intake and exhaustvalve may be operated by an intake cam and an exhaust cam.Alternatively, one or more of the intake and exhaust valves may beoperated by an electromechanically controlled valve coil and armatureassembly. The position of an intake cam may be determined by an intakecam sensor. The position of exhaust cam may be determined by an exhaustcam sensor.

Intake passage 30 may include a throttle 64 having a throttle plate 66.In this particular example, the position of throttle plate 66 may bevaried by controller 12 via a signal provided to an electric motor oractuator included with throttle 64, a configuration that is commonlyreferred to as electronic throttle control (ETC). In this manner,throttle 64 may be operated to vary the intake air provided thecombustion chambers. The position of throttle plate 66 may be providedto controller 12 by throttle position signal TP from a throttle positionsensor 68. Intake passage 30 may include a mass air flow sensor 70 and amanifold air pressure sensor 72 for providing respective signals MAF andMAP to controller 12.

In FIG. 1, fuel injectors are shown coupled directly to the combustionchambers for injecting fuel directly therein in proportion to a pulsewidth of a signal FPW received from controller 12 via an electronicdriver, for example. For example, fuel injectors 74, 76, 78, and 80 areshown in FIG. 1 coupled to cylinders 20, 22, 24, and 26, respectively.In this manner, the fuel injectors provide what is known as directinjection of fuel into the combustion chamber. Each respective fuelinjector may be mounted in the side of the respective combustion chamberor in the top of the respective combustion chamber, for example. In someexamples, one or more fuel injectors may be arranged in intake passage28 in a configuration that provides what is known as port injection offuel into the intake ports upstream of combustion chambers. Though notshown in FIG. 1, fuel may be delivered to the fuel injectors by a fuelsystem including a fuel tank, a fuel pump, a fuel line, and a fuel rail.

The combustion chambers of engine 10 may be operated in a compressionignition mode, with or without an ignition spark. In some examples, adistributorless ignition system (not shown) may provide an ignitionsparks to spark plugs coupled to the combustion chambers in response tocontroller 12. For example, spark plugs 82, 84, 86, and 88 are shown inFIG. 1 coupled to cylinders 20, 22, 24, and 26, respectively.

Engine 10 may include a turbocharger 90. Turbocharger 90 may be includea turbine 92 and a compressor 94 coupled on a common shaft 96. Theblades of turbine 92 may be caused to rotate about the common shaft as aportion of the exhaust gas stream discharged from engine 10 impingesupon the blades of the turbine. Compressor 94 may be coupled to turbine92 such that compressor 94 may be actuated when the blades of turbine 92are caused to rotate. When actuated, compressor 94 may then directpressurized fresh gas to air intake manifold 28 where it may then bedirected to engine 10.

Engine 10 may employ a dual scroll (or twin scroll or two-pulse)turbocharger system 98 wherein at least two separate exhaust gas entrypaths flow into and through turbine 92. A dual scroll turbochargersystem may be configured to separate exhaust gas from cylinders whoseexhaust gas pulses interfere with each other when supplied to turbine92. For example, FIG. 1 shows a first scroll 100 and a second scroll 102which are used to supply separate exhaust streams to turbine 92. Thecross-sectional shape of first scroll 100 and second scroll 102 may beof various shapes, including circular, square, rectangular, D-shaped,etc. Example cross-sections (e.g., end-views) of the first and secondscrolls are illustrated in FIGS. 2-9, discussed below.

For example, if a four-cylinder engine (e.g., an I4 engine such as shownin FIG. 1) has a firing sequence of 1-3-4-2 (e.g., cylinder 20 followedby cylinder 24 followed by cylinder 26 followed by cylinder 22), thencylinder 20 may be ending its expansion stroke and opening its exhaustvalves while cylinder 22 still has its exhaust valves open. In asingle-scroll or undivided exhaust manifold, the exhaust gas pressurepulse from cylinder 20 may interfere with the ability of cylinder 22 toexpel its exhaust gases. However, by using a dual scroll system whereinexhaust ports 40 and 46 from cylinders 20 and 26 are connected to oneinlet of the first scroll 100 and exhaust ports 42 and 44 from cylinders22 and 24 are connected to the second scroll 102, exhaust pulses may beseparated and pulse energy driving the turbine may be increased.

Turbine 92 may include at least one wastegate to control an amount ofboost provided by said turbine. In a dual scroll system, each scroll mayinclude a corresponding wastegate to control the amount of exhaust gaswhich passes through turbine 92. For example, in FIG. 1, the firstscroll 100 includes a first wastegate 104. First wastegate 104 includesa wastegate valve 106 configured to control an amount of exhaust gasbypassing turbine 92. Likewise, the second scroll 102 includes a secondwastegate 108. Second wastegate 108 includes a wastegate valve 110configured to control an amount of exhaust gas bypassing turbine 92.

Exhaust gases exiting turbine 92 and/or the wastegates may pass throughan emission control device 112. Emission control device 112 can includemultiple catalyst bricks, in one example. In another example, multipleemission control devices, each with multiple bricks, can be used. Insome examples, emission control device 112 may be a three-way typecatalyst. In other examples, emission control device 112 may include oneor a plurality of a diesel oxidation catalyst (DOC), selective catalyticreduction catalyst (SCR), and a diesel particulate filter (DPF). Afterpassing through emission control device 112, exhaust gas may be directedto a tailpipe 114.

Engine 10 may include an exhaust gas recirculation (EGR) system 116. EGRsystem 116 may deliver a portion of exhaust gas exiting engine 10 intothe engine air intake passage 30. The EGR system includes an EGR conduit118 coupled to an exhaust passage 122, downstream of the turbine 92, andto the air intake passage 30. In some examples, EGR conduit 118 mayinclude an EGR valve 120 configured to control an amount of recirculatedexhaust gas. As shown in FIG. 1, EGR system 116 is a low pressure EGRsystem, routing exhaust gas from downstream of the turbine 92 toupstream of the compressor 94. In another example, a high pressure EGRsystem may be used in addition to or in place of the low pressure EGRsystem. As such, the high pressure EGR system may route exhaust gas fromone or more of the scrolls 100 and 102, upstream of the turbine 92, tothe intake passage 30, downstream of the compressor 34.

Under some conditions, EGR system 116 may be used to regulate thetemperature and or dilution of the air and fuel mixture within thecombustion chambers, thus providing a method of controlling the timingof ignition during some combustion modes. Further, during someconditions, a portion of combustion gases may be retained or trapped inthe combustion chamber by controlling exhaust valve timing.

In some examples, controller 12 may be a conventional microcomputerincluding: a microprocessor unit, input/output ports, read-only memory,random access memory, keep alive memory, and a conventional data bus.Controller 12 is shown in FIG. 1 receiving various signals from sensorscoupled to engine 10, in addition to those signals previously discussed,including: engine coolant temperature (ECT) from a temperature sensor128; an engine position sensor 130, e.g., a Hall effect sensor sensingcrankshaft position. Barometric pressure may also be sensed (sensor notshown) for processing by controller 12. In some examples, engineposition sensor 130 produces a predetermined number of equally spacedpulses every revolution of the crankshaft from which engine speed (RPM)can be determined. Additionally, various sensors may be employed todetermine turbocharger boost pressure. For example, a pressure sensor132 may be disposed in intake 30 downstream of compressor 94 todetermine boost pressure. Additionally, each scroll of the dual scrollsystem 98 may include various sensors for monitoring operatingconditions of the duel scroll system. For example, the first scroll 100may include an exhaust gas sensor 134 and the second scroll 102 mayinclude an exhaust gas sensor 136. Exhaust gas sensors 134 and 136 maybe any suitable sensor for providing an indication of exhaust gasair/fuel ratio such as a linear oxygen sensor or UEGO (universal orwide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO(heated EGO), a NOx, HC, or CO sensor.

Exhaust gases flowing through the first scroll 100 and exhaust gasesflowing through the second scroll 102 are separated by a dividing wall138. As discussed above, separating the exhaust streams with the firstand second scrolls may increase low end torque and time to torque. Assuch, separating the exhaust gas pulses in this way may, in someexamples, result in an increase in efficiency of exhaust gas delivery toa turbine. However, under some engine operating conditions, separatingexhaust gas pulses as described above may reduce the efficiency ofexhaust gas delivery to the turbine. For example, during high speed andhigh engine load conditions, separating exhaust gas pulses as describedabove may result in an increase in backpressure and pumping work due to,for example, an increase in exhaust gas enthalpy. Thus, this may reducethe engine's power output.

Increasing fluid communication between the first and second scrollsduring high speed and/or load conditions may allow increased engineefficiency and power output. A branch communication valve 140 may bepositioned such that it bridges the first scroll 100 and the secondscroll 102. As such, opening the branch communication valve 140 (e.g.,BCV) may increase fluid communication between the first and secondscrolls. Alternatively, closing the BCV 140 may decrease fluidcommunication between the first and second scrolls. The BCV concepts andembodiments described herein may be used in the dual scrolls within theturbocharger housing assembly and/or in the exhaust passages (e.g.,scrolls as shown in FIG. 1) leading to the inlet of the turbocharger.

Increasing fluid communication may include allowing exhaust gases fromthe first scroll 100 and exhaust gases from the second scroll 102 to mixand enter the opposite scroll. For example, opening the BCV 140 may opena passage or recess between the first and second scrolls. In oneexample, the passage may be positioned in the dividing wall, between thetwo scrolls. In another example, the passage may be positioned on top ofboth scrolls. By opening the BCV valve 140, the exhaust streams may flowthrough the passage, thereby mixing and increasing fluid communicationbetween the scrolls. Example embodiments of the BCV 140 are depicted inFIGS. 2-9, described further below.

FIGS. 2-7 and 9 show different example embodiments of the BCV 140.Specifically, these figures illustrate a first scroll and a secondscroll of a dual scroll turbocharger, fluidically separated by adividing wall. The dual scroll turbocharger further includes a passagepositioned adjacent to the dividing wall and bridging the first scrolland the second scroll and a branch communication valve, positionedwithin the passage and movable between an open position and a closedposition, the open position increasing fluid communication between thefirst scroll and the second scroll.

FIG. 2 shows a first embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 2, the BCV 140 is a side-hingedpoppet valve positioned in an adjacent passage 210. The passage 210 ispositioned adjacent to a dividing wall 138, the dividing wall 138separating a first scroll 100 and a second scroll 102. Specifically, thepassage 210 is positioned on the top of, or vertically above withrespect to a vertical axis 212 parallel to the dividing wall, the firstscroll and the second scroll and bridges the two scrolls. The passage210 includes an opening between the first scroll, the passage, and thesecond scroll. As such, the opening is from the first scroll, across thedividing wall, and to the second scroll. In an alternate example, thepassage 210 may be positioned at the bottom, or vertically below withrespect to the vertical axis 212, the first scroll and the secondscroll.

FIG. 2 includes a side-view 202 of the first embodiment of the BCV 140and passage 210. The side-view 202 shows a side view of one of thescrolls, such as the first scroll 100. The second scroll (not shown inside-view 202) is located behind, with respect to a lateral direction214, the first scroll 100. The BCV 140 comprises a hinge 218 and a valveplate 220 (e.g., plate). The valve plate 220 may open and close bypivoting or rotating around the hinge 218. In the side-view 202, the BCV140 is shown in an open position with the valve plate 220 near the topof the passage 210. Exhaust gases 222 flowing through the first scroll100 and the second flow passage (not shown) may enter the passage 210through an opening 224. The opening 224 bridges both the first scroll100 and the second scroll.

FIG. 2 also includes a top-view 204 of the first embodiment of the BCV140. As discussed above, the passage 210 and the opening 224 bridge boththe first scroll 100 and the second scroll 102. In one example, as shownin FIG. 2, the passage 210 may be centered above (or below in analternate example) the scrolls, along the dividing wall 138. In thetop-view 204, the BCV 140 is closed. Thus, the valve plate 220 engagessealably at the bottom of the passage 210 with the opening 224 such thatexhaust gases 222 from the first scroll 100 and exhaust gases 226 fromthe second scroll 102 may not enter the passage 210. In this position,there may be no fluid communication between the first scroll 100 and thesecond scroll 102.

FIG. 2 further includes a first end-view 206 wherein the BCV 140 isclosed and a second end-view 208 wherein the BCV 140 is open. Exhaustgases 222 and 226 are traveling in the horizontal direction 216 in thefirst scroll 100 and the second scroll 102, respectively. In the firstend-view 206, fluid communication between the scrolls is restricted bythe diving wall 138 and the closed valve plate 220 of BCV 140. In thesecond end-view 208, the BCV 140 is open such that the valve plate 220is not covering the opening 224. As such exhaust gases 224 from thefirst scroll 100 may flow through the passage 210, mix with exhaustgases 226 from the second scroll 102, and enter the second scroll 102.Similarly, exhaust gases 226 from the second scroll 102 may flow throughthe passage 210, mix with exhaust gases 224 from the first scroll 100,and enter the first scroll 100. As such, when the BCV 140 is in the openposition, fluid communication between the two scrolls increases.

The system of FIG. 2 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a passage positioned adjacent to the dividingwall and bridging the first scroll and the second scroll. A branchcommunication valve may be positioned within the passage. The branchcommunication valve may have a plate rotatable about a hinge, the platesealable against an opening between the passage and the first and thesecond scrolls.

FIG. 3 shows a second embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 3, the BCV 140 is a side-hingedpoppet valve positioned between a first scroll 100 and second scroll 102and adjacent to a dividing wall 138. FIG. 3 illustrates a first sideview 302 of the scrolls and the BCV 140 in which the BCV 140 is in aclosed position. FIG. 3 also illustrates a second side view 304 of thescrolls and the BCV 140 in which the BCV 140 is in an opened position.Finally, FIG. 3 illustrates an end-view 306 of the scrolls and the BCV140 in which the BCV 140 is in an opened position.

The BCV 140 comprises a valve plate 308 and a hinge 310, the valve platerotatable about the hinge. The hinge 310 is positioned within a recess312. The recess 312 is positioned within, and at the top of, the secondscroll 102. In another example, the recess may be positioned within, andat the top of, the first scroll 100. In an alternate example, the recessmay be positioned at the bottom of the first or second scroll.

In the closed position, as shown in the first side view 302, the valveplate 308 of the BCV 140 covers an opening 320 in the dividing wall 138.As such, the opening 320 is positioned between the first scroll 100 andthe second scroll 102 such that exhaust gases 322 may pass from onescroll (e.g., first scroll 100), through the opening 320, to theopposite scroll (e.g., second scroll 102). In the closed position,exhaust gases 322 flowing through the first scroll 100, in a horizontaldirection defined by a horizontal axis 318, flow past the opening 320,covered by the valve plate 308. The valve plate 308 may be sealableagainst the dividing wall 138 and opening 320 such that no exhaust gases322 may pass through the opening 320.

To open the BCV 140, the valve plate 308 may rotate around the hinge 310and swing upwards, in a direction shown by arrow 324, into the recess312. This may expose the opening 320 in the dividing wall 138. Theopening 320 may be large enough such that when the BCV 140 is open,exhaust gases 322 may pass through the opening 320, thereby increasingfluid communication between the first scroll 100 and the second scroll102.

In one example, as shown in end-view 306, the recess may be positionedwithin one of the scrolls (e.g., the second scroll 102), at the ceilingor top of the scroll, with respect to the vertical axis 314 and asurface on which the vehicle sits. In this configuration, the valveplate 308 may cover the opening 320 on the second scroll side of thedividing wall 138 when the BCV 140 is in the closed position. In anotherexample, the recess may be positioned within the first scroll and thevalve plate 308 may cover the opening on the first scroll side of thedividing wall 138.

The system of FIG. 3 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a recess positioned within a ceiling of thesecond scroll. Further, the system includes a branch communication valvecomprising a valve plate rotatable about a hinge. The hinge may bepositioned within the recess and the valve plate may be movable betweena first position, wherein the valve plate covers an opening in thedividing wall, and a second position, wherein the valve plate is withinthe recess.

FIG. 4 shows a third embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 4, the BCV 140 is a linear poppetvalve. FIG. 4 includes a first top-view 402 of a first scroll 100, asecond scroll 200, and the BCV 140 in which the BCV 140 is in a closedposition. FIG. 4 also includes a second top-view 404 of the first scroll100, the second scroll 200, and the BCV 140 in which the BCV 140 is inan open position. The top-views are oriented along a lateral axis 414and a horizontal axis 416. The horizontal axis 416 is the direction ofexhaust flow through the scrolls. A vertical axis 412 may be orientedwith respect to a surface on which the vehicle sits.

The BCV 140 comprises a valve plate 420 and a valve stem 418, one end ofthe valve stem coupled to the valve plate. The valve stem 418 ispositioned across one of the scrolls (e.g., first scroll 100 as shown inFIG. 4). Further, the valve stem 418 may fit through a hole in an outerwall 424 of the first scroll 100. The valve stem 418 may be slideablethrough this hole in the outer wall 424 and across the first scroll 100.In an alternate example, the valve stem 418 may be positioned across thesecond scroll 102 and slideable through a hole in an outer wall of thesecond scroll 102.

In a closed position, as shown in the first top-view 402, the valveplate 420 of the BCV 140 covers an opening 410 in the dividing wall 138.In one example, the opening 410 may be circular to match a circularshape of the valve plate 420. In another example, the opening 410 may berectangular or square to match a rectangular or square shape of thevalve plate 420. Further, the valve plate 420 may be sealable againstthe dividing wall 138 such that no exhaust gas may pass through theopening 410. As such, there may be no fluid communication between thefirst scroll 100 and the second scroll 102 when the BCV 140 is in theclosed position.

To open the BCV 140 and allow fluid communication between the first andsecond scrolls, the valve stem 418 may slide in a lateral direction,shown by arrow 422. The valve plate 420 moves with the stem until thevalve plate moves all the way across the first scroll to the outer wall424 of the first scroll. In one example, the valve plate 420 may sitagainst the outer wall 424 to reduce blocking of flow through the firstscroll 100. In another example, the outer wall 424 may have a smallrecess in the shape of the valve plate 420. The valve plate 420 may thenfit within this recess to further reduce flow obstruction in the firstscroll 100. When the BCV 140 is opened, exhaust gases 406 from the firstscroll 100 may flow through the opening 410 and into the second scroll102. Similarly, exhaust gases 408 from the second scroll 102 may flowthrough the opening 410 and into the first scroll 100. In this way,fluid communication between the first and second scrolls may beincreased when the BCV 140 is opened.

The system of FIG. 4 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a branch communication valve comprising a valveplate and valve stem. The valve plate may be slidable from a firstposition, wherein the valve plate covers an opening in the dividingwall, across the first scroll to a second position, wherein the valveplate is adjacent to an outer wall of the first scroll.

FIG. 5 shows a fourth embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 5, the BCV 140 is a swinginggate-type valve positioned adjacent and parallel to a dividing wall 138separating a first scroll 100 and a second scroll 102. FIG. 5 includes afirst top-view 502 in which the BCV 140 is in a closed position. In thisposition, exhaust gases 510 in the first scroll 100 remain separatedfrom exhaust gases 512 in the second scroll 102. Thus, when the BCV 140is in the closed position, there may be no fluid communication orinteraction between the first scroll 100 and the second scroll 102. FIG.5 also includes a second top-view 504 in which the BCV 140 is in an openposition. In this position, exhaust gases 510 in the first scroll 100may flow through an opening 520 in the dividing wall 138 and into thesecond scroll 102. Similarly, exhaust gases 512 in the second scroll 102may flow through the opening 520 and into the first scroll 100. As such,fluid communication between the first scroll 100 and the second scroll102 increases when the BCV 140 is open. The top-views are oriented alonga lateral axis 514 and a horizontal axis 516. The horizontal axis 516 isthe direction of exhaust flow through the scrolls. A vertical axis 518may be oriented with respect to a surface on which the vehicle sits.

The BCV 140 comprises a gate 506 and a hinge 508. The gate 506 isrotatable around the hinge 508, the hinge positioned adjacent thedividing wall 138. In one example, the hinge is positioned within thedividing wall 138. In another example, the hinge is positioned in acavity within the diving wall 138. In yet another example, the hinge 508is positioned on one side of the dividing wall 138. In a first, closedposition, as shown in the first top-view 502, the gate 506 is positionedover (e.g., covering) the opening 520 in the dividing wall 138. The gate506 may be sealable against the dividing wall 138 such that no exhaustgases may pass through the opening 520.

To open the BCV 140 and increase fluid communication between the firstscroll 100 and the second scroll 102, the gate 506 may rotate around thehinge 508 in the direction shown by arrow 522. In an alternate example,the gate 506 may rotate in a direction opposite arrow 522. In a second,open position, as shown in the second top-view 504, the gate 506 ismoved away from the opening 520 such that the opening is exposed andexhaust gases may flow through the opening. In one example, in the openposition, the gate 506 sits against the dividing wall 138. In anotherexample, in the open position, the gate 506 would sit within a creviceor recess in the dividing wall 138 such that the gate would not obstructexhaust gas flow through the first scroll 100. Opening the BCV 140 mayinclude swinging or rotating the gate 506 around the hinge 508 such thatthe gate rotates 180 degrees from a first position on the dividing wall(shown in the first top-view 502) to a second position on the dividingwall (shown in the second top-view 504).

The system of FIG. 5 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a branch communication valve comprising a branchcommunication valve comprising a gate rotatable around a hinge, thehinge positioned adjacent the dividing wall. In one example, the gatemay be movable from a first position on the dividing wall, wherein thegate covers an opening in the dividing wall, to a second position on thedividing wall, the second position opposite the first position withrespect to a position of the hinge.

FIG. 6 shows a fifth embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 6, the BCV 140 is a barrel-typevalve positioned within one of the scrolls. Specifically, FIG. 6 shows afirst end-view 602 of a rectangular flow passage comprising a firstscroll 100 and a second scroll 102. In an alternate example, the flowpassage may be circular. In the first end-view 602, the BCV 140 is in aclosed position such that no exhaust gas flows through a passage oropening 610 between the first scroll 100 and the second scroll 102. Assuch, no fluid communication occurs between the first scroll 100 and thesecond scroll 102. FIG. 6 also shows a second end-view 604 in which theBCV 140 is in an open position. In this position, exhaust gases in thefirst scroll 100 may flow through the opening 610 in the dividing wall138 and into the second scroll 102. Similarly, exhaust gases in thesecond scroll 102 may flow through the opening 610 and into the firstscroll 100. As such, fluid communication between the first scroll 100and the second scroll 102 increases when the BCV 140 is open. Theend-views are oriented along a vertical axis 614 and a lateral axis 616.A horizontal axis 618 depicts the direction of exhaust flow through thescrolls. The vertical axis 614 may be oriented with respect to a surfaceon which the vehicle sits.

The BCV 140 comprises a barrel 608 coupled to a shaft 606. The shaft 606rotates around a rotational axis 612, thereby rotating the barrel withinthe first scroll 100. The barrel 608 may have three closed sides and oneopen side. In a first, closed position (shown in first end-view 602),one of the closed sides is positioned against the dividing wall 138.Specifically, one of the closed sides may be sealable to the dividingwall 138 such that no exhaust gases flow through the opening 610. Theshaft 606 is rotated around the rotational axis 612 to move the BCV 140in to a second, open position (shown in second end-view 604). In thesecond, open position, the one open side of the barrel 608 is positionedagainst the dividing wall 138. In this position, the barrel 608 is nolonger blocking the opening 610. Thus, exhaust gases flowing through thefirst scroll 100 may pass through the opening 610 and into the secondscroll 102. Similarly, exhaust gasses flowing through the second scroll102 may pass through the opening 610 and into the first scroll 100.

The system of FIG. 6 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a branch communication valve comprising a barrelcoupled to a shaft, the shaft rotatable about a rotational axis andwherein rotation of the shaft rotates the barrel from a first position,wherein a closed side of the barrel is positioned adjacent to and coversan opening in the dividing wall, to a second position, wherein an openside of the barrel is positioned adjacent to and does not cover theopening in the dividing wall.

FIG. 7 shows a sixth embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 7, the BCV 140 is a sliding-typepoppet valve positioned within one of the scrolls. FIG. 7 shows a firsttop-view 702 of a first scroll 100, a second scroll 102, and the BCV140. In the first top-view 702, the BCV 140 is in a closed position. Inthe closed position, there may be no fluid communication between thefirst and second scrolls. FIG. 7 also shows a second top-view 704 of thefirst scroll 100, the second scroll 102, and the BCV 140. In the secondtop-view 704, the BCV 140 is in an open position. In the open position,there may be fluid communication between the first and second scrolls.The top-views are oriented along a lateral axis 714 and a horizontalaxis 716. The horizontal axis 716 is the direction of exhaust flowthrough the scrolls. A vertical axis 718 may be oriented with respect toa surface on which the vehicle sits.

The BCV 140 comprises a sliding valve plate 706 coupled to a shaft 708.The shaft 708 is positioned across the first scroll 100. In an alternateexample, the shaft 708 may be positioned across the second scroll 102.As shown in FIG. 7, the shaft 708 is oriented perpendicular to the flowpath of the first scroll 100. In one example, the shaft may bepositioned within the center of the first scroll 100. The shaft 708 mayslide the valve plate 706 along the dividing wall 138. In an alternateembodiment, the valve plate 706 may slide along the shaft 708 to movealong the dividing wall 138.

In a first, closed position (as shown in first top-view 702), the valveplate 706 is positioned adjacent to the dividing wall 138 and covers anopening 710 in the dividing wall. The valve plate may be sealableagainst the dividing wall 138 such that no exhaust gas may pass throughthe opening 710. To open the BCV 140, the shaft 708 slides the valveplate 706 along the dividing wall, in a horizontal direction shown byarrow 712. In a second, open position (as shown in second top-view 704),the valve plate 706 is adjacent to the dividing wall and in a positionfurther down the first scroll 100 on the dividing wall 138, with respectto the direction of exhaust flow. In the open position exhaust gases 510in the first scroll 100 may pass through the opening 710 and into thesecond scroll 102. Similarly, exhaust gases 512 in the second scroll 102may pass through the opening 710 and into the first scroll 100. In thisway, when the BCV 140 is opened, fluid communication between the firstand second scrolls increases.

The system of FIG. 7 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a branch communication valve comprising asliding valve plate positioned adjacent to the diving wall and coupledto a shaft. The shaft may move the sliding valve plate from a firstposition, wherein the valve plate covers an opening in the dividingwall, to a second position, away from, along a horizontal axis, theopening.

FIG. 8 shows a seventh embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 8, the BCV 140 is a rotating valvepositioned within a flow passage 810 (e.g., exhaust flow passage) whichcontains the first scroll 100 and the second scroll 102. An interiordividing wall (e.g., dividing wall 138) separates the exhaust gasestraveling through the first scroll 100 and the second scroll 102. TheBCV 140 in the seventh embodiment has a valve dividing wall 812 whichpartitions a valve body 820 into a first flow chamber 814 and a secondflow chamber 816. The BCV 140 is rotatable about a rotational axis 818.

A first view 802 shows the BCV 140 in a closed position. In the closedposition, the valve dividing wall 812 is in-line with (e.g., parallelto) the dividing wall 138. In this configuration, exhaust gases 822traveling through the first scroll 100 remain separated from the secondscroll 102. For example, exhaust gases traveling through the firstscroll 100 travel only through the first flow chamber 814 and exhaustgases traveling through the second scroll 102 travel only through thesecond flow chamber 816. A front view 804 of the BCV 140 in the closedposition shows a view of the flow passage 810, along the rotational axis808. In this view, only one dividing line (diving wall 138) is seensince the dividing wall 138 of the flow passage 810 is in-line with thevalve dividing wall 812.

A second view 806 shows the BCV 140 in an open position. As shown inFIG. 8, the BCV 140 rotates by 180 degrees, around the rotational axis818, from the closed position to the open position. In alternateembodiments, the open position may be a position less than 180 degreesfrom the closed position. In the open position, the valve dividing wall812 is offset from the dividing wall 138 of the flow passage 810. In theexample shown in FIG. 2, the valve dividing wall 812 and the dividingwall 138 are perpendicular. In this configuration, exhaust gases 822traveling through the first scroll 100 do not remain separated from thesecond scroll 102. For example, exhaust gases traveling through thefirst scroll 100 may enter both the first flow chamber 814 and thesecond flow chamber 816, thereby allowing mixing of exhaust gases andfluid communication between the first scroll 100 and the second scroll102. Gases exiting the valve body 820 through the first flow chamber 814may then flow through the first scroll 100 and the second scroll 102.Likewise, gases exiting the valve body 820 through the second flowchamber 816 may then flow through the first scroll 100 and the secondscroll 102. A front view 808 of the BCV 140 in the open position shows aview of the flow passage 810, along the rotational axis 808. In thisview, both the diving wall 138 and the valve dividing wall 812 are seensince the valve dividing wall 812 is now perpendicular to the dividingwall 138 of the flow passage 810. Thus, rotating the valve body 820around the rotational axis 818 to open the BCV 140 may increase fluidcommunication between the first scroll 100 and the second scroll 102.

The system of FIG. 8 provides for a dual scroll turbocharger systemincluding an exhaust flow passage with an interior dividing wall, theinterior dividing wall partitioning the flow passage into a first scrolland a second scroll. The system further includes a branch communicationvalve positioned within the exhaust flow passage. The branchcommunication valve may comprise a first chamber and a second chamberseparated by a valve dividing wall. Further, the branch communicationvalve may be rotatable around a rotational axis.

FIG. 9 shows a eighth embodiment of the branch communication valvedepicted in FIG. 1. As shown in FIG. 9, the BCV 140 is a sliding valvepositioned within a dividing wall 138. The dividing wall separates afirst scroll 100 and a second scroll 102. The BCV 140 comprises acylindrical block 908 slideable between an open, closed, or plurality ofintermediate positions between fully open and fully closed. A first sideview 902 shows the BCV 140 in a closed position. In the closed positionthere may be no fluid communication between the first scroll 100 andsecond scroll 102. A second side view 906 shows the BCV 140 in an openposition. In the open position exhaust gases may pass through an opening922 in the dividing wall 138, thereby allowing fluid communicationbetween the first scroll 100 and the second scroll 102. A front view 904shows a position of the BCV 140 within the dividing wall 138. As shownin this view, the BCV 140 may be centered along the dividing wall 138.Thus, the BCV 140 separates the first scroll 100 from the second scroll102.

As shown in the first side view 902 and the second side view 906, thecylindrical block 908 is coupled at a first end to a first end of aspring 910. A second end of the spring 910 is coupled to a firstinterior wall 912. The first interior wall 912 is positioned within acavity 914 within the dividing wall 138. The cavity 914 is formed by thefirst interior wall 912, a second interior wall 916, a first sideinterior wall 918, and a second side interior wall 920. In a closedposition (as shown in first side view 902), a second end of thecylindrical block 908 is sealable against the second interior wall 916.

In one example, the BCV 140 may be a passive sliding valve wherein apressure of the exhaust flow traveling through the first scroll 100 andthe second scroll 102 determines a position of the BCV 140. For example,when the flow pressure on a front surface 926 (shown in front view 904)of the BCV 140 (and cylindrical block 908) is below a thresholdpressure, the valve may remain closed. The threshold pressure may bebased on a stiffness, or spring constant, of the spring 910. Forexample, if the stiffness of the spring 910 increases, the thresholdpressure may also increase. As such, a high flow pressure is required toopen the valve. Alternatively, when the flow pressure on the frontsurface 926 is greater than the threshold pressure, the cylindricalblock 908 may be pushed along with the exhaust gas flow 928.Specifically, the cylindrical block 908 may slide into the cavity 914,in a horizontal direction, as shown by arrow 924. As the cylindricalblock 908 slides into the cavity 914, the spring 910 compresses againstthe first interior wall 912. As a result, an opening 922 increases inthe dividing wall 138. The opening 922 allows exhaust gases from thefirst scroll 100 to enter the second scroll and exhaust gases from thesecond scroll 102 to enter the first scroll 100.

The system of FIG. 9 provides for a dual scroll turbocharger systemincluding a first scroll and a second scroll. The first scroll and thesecond scroll may be fluidically separated by a dividing wall. Thesystem further includes a cavity positioned within the dividing wall anda branch communication valve positioned within the cavity. The branchcommunication valve may comprise a cylindrical block coupled to a firstend of a spring, a second end of the spring coupled to an interior wallof the cavity. The cylindrical block may be slidable within the cavitybetween a sealed, closed, position and an open position. When in theopen position, an opening between the first scroll and the second scrollis created, thereby fluidically combining the two scrolls. When in theclosed position, the cylindrical block is sealable against a secondinterior wall. Further, the cylindrical block may slide from the closedposition to the open position when a flow pressure of an exhaust flowtraveling through the first scroll and the second scroll increases abovea threshold pressure and wherein the threshold pressure is based on astiffness of the spring.

In this way, a branch communication valve may be opened or closed toincrease or decrease fluid communication between a first scroll and asecond scroll of a twin scroll turbocharger. In one example, the branchcommunication valve may be positioned within a flow passage, the flowpassage positioned adjacent a dividing wall separating the first scrolland the second scroll. Further, an opening in the flow passage maybridge the first scroll and the second scroll such that exhaust gasesfrom the two scrolls may enter the flow passage and the opposite scrollwhen the branch communication valve is opened. In another example, thebranch communication valve may be positioned within the dividing wall.In a closed position, the branch communication valve may cover andopening within the dividing wall, between the first and second scrolls.In an open position, the branch communication valve may expose theopening such that exhaust gases from the first scroll may enter thesecond scroll and exhaust gases from the second scroll may enter thefirst scroll. The branch communication valve may be of various types,including a side-hinged poppet valve, a linear poppet valve, a swinginggate-type valve, a sliding poppet valve, a barrel-type valve, a rotatingvalve, and/or a sliding valve (within a cavity in the dividing wall). Inthis way, the branch communication valve may increase or decrease fluidcommunication between a first and second scroll in a dual scrollturbocharger.

Note that the example control routines included herein can be used withvarious engine and/or vehicle system configurations. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various acts,operations, or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedacts or functions may be repeatedly performed depending on theparticular strategy being used. Further, the described acts maygraphically represent code to be programmed into the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. Further, one or moreof the various system configurations may be used in combination with oneor more of the described diagnostic routines. The subject matter of thepresent disclosure includes all novel and non-obvious combinations andsub-combinations of the various systems and configurations, and otherfeatures, functions, and/or properties disclosed herein.

The invention claimed is:
 1. A dual scroll turbocharger system,comprising: a dividing wall positioned in an exhaust gas passage betweenand separating a first fluid flow through a first scroll and a secondfluid flow through a second scroll; a branch communication valve movablebetween an open and a closed position; a passage connects the firstfluid flow and the second fluid flow, and the first and second fluidflows extending upstream and downstream of the passage; and the branchcommunication valve in the closed position extends parallel to the firstand second fluid flows and blocks the passage, wherein pressure withinthe first scroll, the second scroll, or both moves the branchcommunication valve into the open position.
 2. The dual scrollturbocharger system of claim 1, wherein the branch communication valveis positioned adjacent to the first and second scrolls and the passageis positioned along an external wall of the first and second scrolls. 3.The dual scroll turbocharger system of claim 1, wherein the branchcommunication valve and passage are positioned on the dividing wall, andthe branch communication valve is parallel with the dividing wall in theclosed position.
 4. The dual scroll turbocharger system of claim 1,wherein the branch communication valve comprises a hinge and plate, andthe hinge is positioned on the dividing wall.
 5. The dual scrollturbocharger system of claim 1, wherein fluid flow through the passageis perpendicular to the first and second fluid flows through the firstand second scrolls, and fluid flow past the branch communication valvein the closed position is parallel to the branch communication valve. 6.The dual scroll turbocharger system of claim 1, wherein the branchcommunication valve comprises a valve plate and valve stem, and thevalve plate extending parallel to the first and second fluid flows inthe closed position.
 7. The dual scroll turbocharger system of claim 1,wherein in the closed position, the branch communication valve does notblock the first and second fluid flows downstream of the branchcommunication valve.
 8. The dual scroll turbocharger system of claim 1,wherein a valve plate of the branch communication valve extends toward acentral axis of the first or second scroll when the branch communicationvalve is in the open position.
 9. The dual scroll turbocharger system ofclaim 1, wherein a valve plate of the branch communication valve movesin a direction parallel to the dividing wall and downstream of the firstfluid flow or the second fluid flow to the open position within thefirst scroll or the second scroll.
 10. A dual scroll turbochargersystem, comprising: a dividing wall positioned between and separating afirst fluid flow of a first scroll and a second fluid flow of secondscroll of the turbocharger system; a passage connecting the first andsecond fluid flows of the first and the second scrolls, and the firstand second fluid flows extend upstream and downstream of the passage; abranch communication valve in a closed position seals the passage andextends parallel to the first and second flows upstream of the branchcommunication valve; and a valve plate of the branch communication valvemoves in a direction parallel to the dividing wall to an open positionwithin the first scroll or the second scroll and a portion of the branchcommunication valve is a distance away from an entrance to the passagewhen the branch communication is in an open position.
 11. The dualscroll turbocharger system of claim 10, wherein the passage is anopening through the dividing wall and the branch communication valveextends across the opening.
 12. The dual scroll turbocharger system ofclaim 10, wherein in the closed position, the branch communication valvedoes not block the first and second fluid flows downstream of the branchcommunication valve.
 13. The dual scroll turbocharger system of claim10, wherein pressure within the first scroll, second scroll, or bothmove the branch communication valve into the open position.
 14. A dualscroll turbocharger system, comprising: a dividing wall positionedbetween and separating a first fluid flow of a first scroll and a secondfluid flow of a second scroll; a passage connecting the first and secondfluid flows, and the first and second fluid flows extending upstream anddownstream of the passage; in a closed position, a branch communicationvalve is positioned covering an entrance to the passage but allows thefirst and second fluid flows to flow downstream of the branchcommunication valve into each of the first and second scrolls; and in anopen position, at least one edge of the branch communication valve isseparated from an edge of the dividing wall defining the entrance to thepassage, wherein pressure within the first scroll, the second scroll, orboth moves the branch communication valve into the open position. 15.The dual scroll turbocharger system of claim 14, wherein a valve plateof the branch communication valve is positioned parallel to the firstand second fluid flows of the first and second scrolls in the open andclosed position.
 16. The dual scroll turbocharger system of claim 14,wherein the branch communication valve is part of the dividing wall. 17.The dual scroll turbocharger system of claim 16, wherein the passagepasses through the dividing wall, and the branch communication valve isrotated about a central axis, the central axis positioned within thepassage.
 18. The dual scroll turbocharger system of claim 14, whereinthe branch communication valve moves between the open and closedpositions in a direction parallel with the dividing wall.
 19. The dualscroll turbocharger system of claim 18, wherein the branch communicationvalve is connected to a spring.
 20. The dual scroll turbocharger systemof claim 14, wherein a valve plate of the branch communication valve ispositioned parallel to, alongside of the dividing wall and within thefirst scroll or the second scroll when the branch communication valve isin the open position.